COMPOUNDS | ELECTRICALLY CONDUCTIVE
Right: HDPE- graphene masterbatch from Graph- matech
tivity without “hot spots” in the range of 105
–109
ohm·cm, while retaining the original key mechanical properties, such as durability and strength, and minimally impacting the host polymer matrix, according to OCSiAl. “Further- more, a low working dosage of 0.1-0.3 wt.% of graphene nanotubes demonstrates only a limited effect on rheological properties and processability,” it claims. “The working loading of graphene nanotubes is significantly lower than the dosage required for multi walled carbon nanotubes: typically 0.1–0.3 wt.% compared to 1–5 wt.% ,” says Christian Maus, Development and Support Leader for Thermoplas- tics, OCSiAl Group. “This gives a number of benefits. Feedback from our customers shows that Tuball graphene nanotubes can be used to prepare compounds with overall high mechanical perfor- mance and allow easier moulding of complex parts compared to products with MWCNTs.” OCSiAl’s carbon nanotubes are already being used commercially in automotive body parts. Russian compounder R&P PolyPlastic developed its Armamid conductive glass-filled PA66, which offers conductivity in the range of 106
to 108 Ω cm, using
the company’s Tuball Matrix 826 grade. Since last year, a conductive Armamid compound been used to produce on-line painted fenders for the GAZ Gazelle NN light commercial truck.
Graphene developments Sweden’s Graphmatech, based in Upsalla, is building up a range of conductive masterbatches and compounds containing graphenes for injection moulding, extrusion and FFF 3D printing applica- tions. Torkel Nord Bjärneman, Business Develop- ment Manager for its Polymer Division, says the company dates back to 2017 at Uppsala University where researcher Mamoun Taher invented Aros Graphene, which he describes as a unique gra- phene hybrid material. According to the company, when produced on a
large scale, the individual one-molecule-thick layers in pure graphene have a tendency to stick together, making the material more like a graphite. Aros Graphene is said to have been designed to
This “dark box” is produced in an AvanShield graphene-filled compound from Avanzare to protect sensitive electronics
IMAGE: AVANZARE INNOVACION TECNOLOGICA 52 COMPOUNDING WORLD | February 2022
www.compoundingworld.com
prevent this by incorporating specially designed “separator” molecules. Graphmatech performs some of its graphene
production in-house and outsources other grades. “We utilise a robust supply-chain of graphene suppliers, as there are many different forms of graphene with different end-applications,” says Bjärneman. “We normally functionalise the flakes in-house using a patented process, to make the graphene flakes compatible with the polymer and to avoid re-agglomeration of the flakes.” Bjärneman says that for polymer-graphene
formulations it uses a “few-layer graphene flakes with a certain average thickness, lateral size, and layer count.” These are produced using graphite as the feedstock material. “We usually speak of multifunctionality when we talk about added benefit, because graphene can enable applications where for example the me- chanical, thermal properties and processability are just as critical as the electrical properties,” he says. “We can see that graphene reaches percolation
at lower concentrations than carbon black. That means that a lot less graphene is required to achieve the dissipative properties of carbon black. At the concentration where carbon black shows dissipative properties, graphene is already enter- ing the conductive region. This unlocks more possibilities beyond static charge dissipation,” Bjärneman claims. Cost is, of course, a concern for compound developers. “We analyse the added cost per kilo of compound,” he says. “Today, we sell solutions with an added cost similar to solutions using carbon nanotubes. Once demand increases, and production volumes increases, we expect a similar added cost as high-conductive carbon black, which will open up more applications.” Graphene and other nanoparticles are
used in the AvanShield range of EMI/RFI shielding compounds from Avanzare Innova-
IMAGE: GRAPHMATECH
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